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Friday
Jun262009

PlentyOfFish Architecture

Update 5: PlentyOfFish Update - 6 Billion Pageviews And 32 Billion Images A Month
Update 4: Jeff Atwood costs out Markus' scale up approach against a scale out approach and finds scale up wanting. The discussion in the comments is as interesting as the article. My guess is Markus doesn't want to rewrite his software to work across a scale out cluster so even if it's more expensive scale up works better for his needs.
Update 3: POF now has 200 million images and serves 10,000 images served per second. They'll be moving to a 250,000 IOPS RamSan to handle the load. Also upgraded to a core database machine with 512 GB of RAM, 32 CPU’s, SQLServer 2008 and Windows 2008.
Update 2: This seems to be a POF Peer1 love fest infomercial. It's pretty content free, but the production values are high. Lots of quirky sounds and fish swimming on the screen.
Update: by Facebook standards Read/WriteWeb says POF is worth a cool one billion dollars. It helps to talk like Dr. Evil when saying it out loud.

PlentyOfFish is a hugely popular on-line dating system slammed by over 45 million visitors a month and 30+ million hits a day (500 - 600 pages per second). But that's not the most interesting part of the story. All this is handled by one person, using a handful of servers, working a few hours a day, while making $6 million a year from Google ads. Jealous? I know I am. How are all these love connections made using so few resources?

Site: http://www.plentyoffish.com/

Information Sources

  • Channel9 Interview with Markus Frind
  • Blog of Markus Frind
  • Plentyoffish: 1-Man Company May Be Worth $1Billion

    The Platform

  • Microsoft Windows
  • ASP.NET
  • IIS
  • Akamai CDN
  • Foundry ServerIron Load Balancer

    The Stats

  • PlentyOfFish (POF) gets 1.2 billion page views/month, and 500,000 average unique logins per day. The peak season is January, when it will grow 30 percent.
  • POF has one single employee: the founder and CEO Markus Frind.
  • Makes up to $10 million a year on Google ads working only two hours a day.
  • 30+ Million Hits a Day (500 - 600 pages per second).
  • 1.1 billion page views and 45 million visitors a month.
  • Has 5-10 times the click through rate of Facebook.
  • A top 30 site in the US based on Competes Attention metric, top 10 in Canada and top 30 in the UK.
  • 2 load balanced web servers with 2 Quad Core Intel Xeon X5355 @ 2.66Ghz), 8 Gigs of RAM (using about 800 MBs), 2 hard drives, runs Windows x64 Server 2003.
  • 3 DB servers. No data on their configuration.
  • Approaching 64,000 simultaneous connections and 2 million page views per hour.
  • Internet connection is a 1Gbps line of which 200Mbps is used.
  • 1 TB/day serving 171 million images through Akamai.
  • 6TB storage array to handle millions of full sized images being uploaded every month to the site.

    What's Inside

  • Revenue model has been to use Google ads. Match.com, in comparison, generates $300 million a year, primarily from subscriptions. POF's revenue model is about to change so it can capture more revenue from all those users. The plan is to hire more employees, hire sales people, and sell ads directly instead of relying solely on AdSense.
  • With 30 million page views a day you can make good money on advertising, even a 5 - 10 cents a CPM.
  • Akamai is used to serve 100 million plus image requests a day. If you have 8 images and each takes 100 msecs you are talking a second load just for the images. So distributing the images makes sense.
  • 10’s of millions of image requests are served directly from their servers, but the majority of these images are less than 2KB and are mostly cached in RAM.
  • Everything is dynamic. Nothing is static.
  • All outbound Data is Gzipped at a cost of only 30% CPU usage. This implies a lot of processing power on those servers, but it really cuts bandwidth usage.
  • No caching functionality in ASP.NET is used. It is not used because as soon as the data is put in the cache it's already expired.
  • No built in components from ASP are used. Everything is written from scratch. Nothing is more complex than a simple if then and for loops. Keep it simple.
  • Load balancing
    - IIS arbitrarily limits the total connections to 64,000 so a load balancer was added to handle the large number of simultaneous connections. Adding a second IP address and then using a round robin DNS was considered, but the load balancer was considered more redundant and allowed easier swap in of more web servers. And using ServerIron allowed advanced functionality like bot blocking and load balancing based on passed on cookies, session data, and IP data.
    - The Windows Network Load Balancing (NLB) feature was not used because it doesn't do sticky sessions. A way around this would be to store session state in a database or in a shared file system.
    - 8-12 NLB servers can be put in a farm and there can be an unlimited number of farms. A DNS round-robin scheme can be used between farms. Such an architecture has been used to enable 70 front end web servers to support over 300,000 concurrent users.
    - NLB has an affinity option so a user always maps to a certain server, thus no external storage is used for session state and if the server fails the user loses their state and must relogin. If this state includes a shopping cart or other important data, this solution may be poor, but for a dating site it seems reasonable.
    - It was thought that the cost of storing and fetching session data in software was too expensive. Hardware load balancing is simpler. Just map users to specific servers and if a server fails have the user log in again.
    - The cost of a ServerIron was cheaper and simpler than using NLB. Many major sites use them for TCP connection pooling, automated bot detection, etc. ServerIron can do a lot more than load balancing and these features are attractive for the cost.
  • Has a big problem picking an ad server. Ad server firms want several hundred thousand a year plus they want multi-year contracts.
  • In the process of getting rid of ASP.NET repeaters and instead uses the append string thing or response.write. If you are doing over a million page views a day just write out the code to spit it out to the screen.
  • Most of the build out costs went towards a SAN. Redundancy at any cost.
  • Growth was through word of mouth. Went nuts in Canada, spread to UK, Australia, and then to the US.
  • Database
    - One database is the main database.
    - Two databases are for search. Load balanced between search servers based on the type of search performed.
    - Monitors performance using task manager. When spikes show up he investigates. Problems were usually blocking in the database. It's always database issues. Rarely any problems in .net. Because POF doesn't use the .net library it's relatively easy to track down performance problems. When you are using many layers of frameworks finding out where problems are hiding is frustrating and hard.
    - If you call the database 20 times per page view you are screwed no matter what you do.
    - Separate database reads from writes. If you don't have a lot of RAM and you do reads and writes you get paging involved which can hang your system for seconds.
    - Try and make a read only database if you can.
    - Denormalize data. If you have to fetch stuff from 20 different tables try and make one table that is just used for reading.
    - One day it will work, but when your database doubles in size it won't work anymore.
    - If you only do one thing in a system it will do it really really well. Just do writes and that's good. Just do reads and that's good. Mix them up and it messes things up. You run into locking and blocking issues.
    - If you are maxing the CPU you've either done something wrong or it's really really optimized. If you can fit the database in RAM do it.
  • The development process is: come up with an idea. Throw it up within 24 hours. It kind of half works. See what user response is by looking at what they actually do on the site. Do messages per user increase? Do session times increase? If people don't like it then take it down.
  • System failures are rare and short lived. Biggest issues are DNS issues where some ISP says POF doesn't exist anymore. But because the site is free, people accept a little down time. People often don't notice sites down because they think it's their problem.
  • Going from one million to 12 million users was a big jump. He could scale to 60 million users with two web servers.
  • Will often look at competitors for ideas for new features.
  • Will consider something like S3 when it becomes geographically load balanced.

    Lessons Learned

  • You don't need millions in funding, a sprawling infrastructure, and a building full of employees to create a world class website that handles a torrent of users while making good money. All you need is an idea that appeals to a lot of people, a site that takes off by word of mouth, and the experience and vision to build a site without falling into the typical traps of the trade. That's all you need :-)
  • Necessity is the mother of all change.
  • When you grow quickly, but not too quickly you have a chance grow, modify, and adapt.
  • RAM solves all problems. After that it's just growing using bigger machines.
  • When starting out keep everything as simple as possible. Nearly everyone gives this same advice and Markus makes a noticeable point of saying everything he does is just obvious common sense. But clearly what is simple isn't merely common sense. Creating simple things is the result of years of practical experience.
  • Keep database access fast and you have no issues.
  • A big reason POF can get away with so few people and so little equipment is they use a CDN for serving large heavily used content. Using a CDN may be the secret sauce in a lot of large websites. Markus thinks there isn't a single site in the top 100 that doesn’t use a CDN. Without a CDN he thinks load time in Australia would go to 3 or 4 seconds because of all the images.
  • Advertising on Facebook yielded poor results. With 2000 clicks only 1 signed up. With a CTR of 0.04% Facebook gets 0.4 clicks per 1000 ad impressions, or .4 clicks per CPM. At 5 cent/CPM = 12.5 cents a click, 50 cent/CPM = $1.25 a click. $1.00/CPM = $2.50 a click. $15.00/CPM = $37.50 a click.
  • It's easy to sell a few million page views at high CPM’s. It's a LOT harder to sell billions of page views at high CPM’s, as shown by Myspace and Facebook.
  • The ad-supported model limits your revenues. You have to go to a paid model to grow larger. To generate 100 million a year as a free site is virtually impossible as you need too big a market.
  • Growing page views via Facebook for a dating site won't work. Having a visitor on you site is much more profitable. Most of Facebook's page views are outside the US and you have to split 5 cent CPM’s with Facebook.
  • Co-req is a potential large source of income. This is where you offer in your site's sign up to send the user more information about mortgages are some other product.
  • You can't always listen to user responses. Some users will always love new features and others will hate it. Only a fraction will complain. Instead, look at what features people are actually using by watching your site.

    Related Articles

  • MySpace also uses Windows to run their site.
  • Markus Frind's posts on Webmaster World.
  • And the Money Comes Rolling In by Max Chafkin
  • How I started A Dating Empire by Markus Frind

    Thanks to Erik Osterman for recommending profiling PlentyOfFish.
  • Reader Comments (67)

    I wish I new. Why do good sites die when other lessor sites thrive? The answer has to do with Paris Hilton somehow, I am just not sure what it is.

    November 29, 1990 | Unregistered CommenterTodd Hoff

    Its about dating .. and u know where everyone hopes it leads to in their own different ways. The same why everyone gawks at Paris Hilton and her doings .. all u need is a reliable site and no interference and the lottery word of mouth ie someone won a million here and there

    November 29, 1990 | Unregistered CommenterAnonymous

    "IIS arbitrarily limits the total connections to 64,000 so a load balancer was added to handle the large number of simultaneous connections."

    I'm glad that was cleared up. When the author of plentyoffish made the original post about his setup, there was a lot of vagueness. He made claims in the comments that 64k was a hard number due to the number of ports in TCP. It took a lot of arguing (and I don't think he was ever convinced in that thread) to tell him that the TCP spec doesn't limit the number of possible TCP connections by the number of available ports -- there is a near infinite number of simultaneous connections. The bottleneck is how many the operating system and hardware can handle. :)

    IIS is quirky if it simply limits the number of connections arbitrarily. It's almost as bad as the original idea that "64k is more than anyone will need" (paraphrased). And the idea that HDDs will never be bigger than 2GB. And so forth.

    IIS does have one major advantage -- it is tied very closely to the OS it runs on. It probably enjoys the benefit of kernel-space IO which is much faster than user-space. It's hard to believe that no caching is being used at all; but it's not impossible.

    Ultimately you can never tell. This guy could be lying through his teeth.

    November 29, 1990 | Unregistered CommenterJ Kenneth King

    I'm not sure I understand the "do only reads or only writes".

    How do I update the database without writes. Replicate changes to another database?

    November 29, 1990 | Unregistered Commenterfisher

    > How do I update the database without writes. Replicate changes
    > to another database?

    Yes. And in that database you can use a denormalized schema and more access oriented indexes. You also don't need to have triggers because the data should be verified on the write database. Maybe you can use different table types, caching policies, and other read optimizations as well.

    November 29, 1990 | Unregistered CommenterTodd Hoff

    its a TCP/IP limitation. NAT only supports 64,000 connections per Source IP address. Its nothing to do with IIS its TCP/IP related.

    http://www.foundrynet.com/services/documentation/sixl/slb.html

    The SI supports a maximum of 64,000 simultaneous connections on each source IP address. This maximum value is based on the architectural limits of IP itself. As a result, if you add only one source IP address, the SI can support up to a maximum of 64,000 simultaneous connections to the real servers. If you configure 64 source IP addresses, the SI can support more simultaneous connections.

    November 29, 1990 | Unregistered CommenterAnonymous

    For startup like Markus, what is the best hosting option (and grow more later)? host your own server or use ISP co-location option?
    He still has to pay huge money on the bandwidth with that payload, right?

    November 29, 1990 | Unregistered CommenterAnonymous

    as far as Iam concerned pof really stands for plenty of fuckwits Marckus is a pathetic back stabbing prick , they never answer you questions they just delete you for no reason , they make up the rules as they go along , and when you do the right thing you are victimised for it , I had made some great friends , the pricks at POF deleted all my pics and threated me , my pics complied well within the rules , then the cock suckers deleted my profile and when i tired to contact them , yep you guessed it no answer , I realise iam not all that polite right now but my emails have been to them well not any more I think all the hackers should unite and murder this site out of its shitful existance , they have a thing called customer care , yeah well thats bullshit as well , the only thing they care about is fucking you over and over and over sad sad sad oh so sad that such small minds cannot maintain there sad site , they could not even maintain a garbage bin let alone earn the trust of the public , they are just a pack of pretenders , wannbes it really is a sad service thats not worth a pinch of shit well it really is Plenty of FUCKWITS

    November 29, 1990 | Unregistered CommenterAnonymous

    Yes you seem to be a likable person. To bad this sort of thing always happen to the nicest people.

    November 29, 1990 | Unregistered CommenterAnonymous

    Hey I found a website that sounds just like his lol. Its called plenty of torrents. Its for searching torrent files. What do you think? Would you rather date a creepy guy off there or download some good old porn. :)

    here it is http://www.plentyoftorrents.com

    I wonder if he knows about it or is going to sue them? lol

    November 29, 1990 | Unregistered CommenterAnonymous

    Wow, Markus made a really cheap solution for site with so high popularity.

    November 29, 1990 | Unregistered CommenterAlexei A. Korolev

    He probably has a giant brain or something.

    November 29, 1990 | Unregistered CommenterAnonymous

    There is a cool book that can help answering the question: "Why do good sites die when other lessor sites thrive?". It's called Made to Stick, and the subtitle reads: "Why some ideas survive and others die".
    The authors state that the 6 properties of a sticky idea are: http://www.madetostick.com/thebook/excerpts.php">Simplicity, Unexpectedness, Concreteness, Credibility, Emotive and Story.
    As site ideas go I would add that the site must provide minimal barriers to entry: no sign up necessary for trying out the site and start off with a good ui interface. If we combine this with a carefully crafted idea (and a scalable architecture) word of mouth can take a site a long way. :)

    As for POF... WoW! It is very cool to know that one (1!!) person can get such a high traffic site going! Congrats to Markus! :)

    November 29, 1990 | Unregistered CommenterDavide Marquês

    In re: to this comment: "IIS does have one major advantage -- it is tied very closely to the OS it runs on. It probably enjoys the benefit of kernel-space IO which is much faster than user-space. It's hard to believe that no caching is being used at all; but it's not impossible."

    Read an older article I wrote about Apache vs. IIS, where I specifically address this:

    http://techxworld.com/community/blogs/features/archive/2007/02/25/apache-vs-iis.aspx

    You can do something very similar to IIS and HTTP.sys with tools such as phhttpd.

    --
    Dustin Puryear
    Author, Best Practices for Managing Linux and UNIX Servers
    http://www.puryear-it.com/pubs/linux-unix-best-practices

    November 29, 1990 | Unregistered CommenterDustin Puryear

    Very informative article, great job!

    There's one thing though I'm not really sure of, you mention that everything is dynamic, no static contents is served, how do explain then that every profile on the site has a .htm extension and no query string?
    e.g.
    http://www.plentyoffish.com/member1793945.htm

    Everything else on the site has the extension .aspx though!

    This seems like static to me .. no database trips or ASP.NET pipeline (ie. no ASP.NET objects are created for every request) just IIS serving static pages (with server includes though) and with file caching in Windows, you could have as many files cached and you won't even have to read them from the hard drive (let's say a file is from 30k to 50k average and with the amount of memory he's got in his servers - many gigas as you mention here - you can have all or most profiles cached), if you check the newest members on the site you'll find that they have a number more than 6 millions which means he's got more than 6 million members (so this means a little over 6 million files/profiles) .. or how else do you think you can serve millions of profiles without using any caching?! Just some thoughts of mine, I would be very interested to hear what you think...

    Wal

    you forgot about mod_rewrite. you have rewrite you query string into something more Search Engine friendly.

    November 29, 1990 | Unregistered CommenterTchibo

    I understand that the URLs can be rewritten but just having everything in .aspx except the profiles has got to make you think .. of course I can't be sure of all of this, it's just a hunch that tells me this is done for a reason ..

    Why waiting for S3 when there are many other CDN's out there with multiple geographic locations around the world :)

    November 29, 1990 | Unregistered CommenterValueCDN

    I'd assume that you're talking about your site :)

    November 29, 1990 | Unregistered Commenter.NET Developer Sydney

    I agree. I think there is some hidden trick besides just world of mouth. I mean other free sites have been around longer but for some reason aren't as lucky http://www.oliveyou.net. I read in another blog he filled up the profiles with fake posts until it got rolling. I don't know if that is believable or not. What is the trick to get to the critical mass where it starts to feed upon itself?

    Re: DEATH TO POF
    How much did you pay for it? What have you lost? Think about and then consider how you would have handled the situation from the other side, but with 100 other people like yourself.

    November 29, 1990 | Unregistered CommenterFree Dating Personals

    I also recommend the book "The Tipping Point"--- talks about mavens and mavericks, and connectors, and how viral ideas (memes) spread like the iPod and hipster loafers.

    November 29, 1990 | Unregistered Commenter100% Free

    What do you think about Disk space for POF and Database storage space for POF ?
    Is it in TBs ?

    November 29, 1990 | Unregistered CommenterJani

    Maybe they deleted you because your illiterate? Isn't that in their terms and conditions? I would add that to my terms and conditions if I had people like you sign up on my site. Moron.

    The thought that you take that much effort to vent about POF is ridiculous. Do you think we care? Really, do you? No. We're talking about server architecture.

    November 29, 1990 | Unregistered CommenterAnonymous

    I think you're deadon about the mod_rewrite. He would HAVE TO. This was probably a key point in increasing his SEO.

    Hey can anyone recommend a good capcha text anti bot script like on this website below required for entering a response?

    November 29, 1990 | Unregistered CommenterAnonymous

    Hey Todd,

    Can you break that down into English? I'm very interested in learning what you mean :)

    November 29, 1990 | Unregistered CommenterMax

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